Supported catalyst composition for polymerization of olefins, method for preparing the same and process for polymerization using the same

ABSTRACT

Supported catalyst composition for polymerization of olefins comprising: (i) a titanium compound, a magnesium compound and at least one electron donor compound; (ii) a chlorine containing polymer support; and (iii) a cocatalyst comprising at least one aluminum compound, wherein the magnesium loading on the final catalyst is between about 0.20 and 6% by weight.

This application is the national stage of PCT/IB02/02832, filed Jan. 7,2002, which claims priority under 35 U.S.C. §119 based on EP 01102891.7,filed Feb. 15, 2001.

FIELD OF THE INVENTION

The present invention relates to a supported catalyst composition forpolymerization of olefins, a method for preparing the same and a processfor polymerization using the same.

DESCRIPTION OF THE PRIOR ART

Supported heterogeneous catalyst compositions for the polymerization ofolefins are well known in the art.

In many cases, silica supported titanium based catalysts have been usedfor the polymerization of olefins. However, their use does result in thepresence of impurities in the final product. These impurities, in turn,cause the polymer to have an poor film appearance rating. Thus, whilesilica supported catalysts provide good particle morphology, a sacrificeis made in the quality of the polymer.

Therefore, a need existed to provide catalyst supports overcoming thedrawbacks of using silica.

L. Sun, C. C. Hsu and D. W. Bacon, Journal of Polymer Science: Part APolymer Chemistry, Vol. 32, 2127–2134, describe eleven polymers ofdifferent backbone structures and functional groups which are tested fortheir suitability for use as a catalyst support.

U.S. Pat. No. 5,102,841 discloses the use of polypropylene polymer assupport to bond particulate of catalyst precursor based on titanium orvanadium. A catalyst preparation is used therein for a catalystprecursor which is already described in U.S. Pat. No. 4,303,771. In U.S.Pat. No. 5,102,841 a process for the production of polyethylene isdisclosed utilizing a catalyst having a support which furnishes aparticle morphology equivalent to silica and other organic oxidesupports, but essentially avoids the presence of objectionable residuein the resin. The process of U.S. Pat. No. 5,102,841 comprisescontacting ethylene or a mixture comprising ethylene and one or morealpha-olefins and, optionally, one or more diolefins, underpolymerization conditions with a catalyst system comprising:

-   (a) a particulate catalyst precursor containing titanium and/or    vanadium.-   (b) polypropylene support particles to which the catalyst precursor    particles are bonded; and-   (c) a hydrocarbyl aluminum cocatalyst.

However, use of the process of U.S. Pat. No. 5,102,841 will result in alow productivity for that catalyst composition. Moreover, a productclarity and resin morphology are obtained which are not satisfying.Further, the catalyst price is quite high.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a supported catalystcomposition, which overcomes the drawbacks of the prior art, especiallyimproving its productivity.

It is a further object of the present invention to provide a method forpreparing such a supported catalyst composition with lower costs.

It is still a further object of the present invention to provide aprocess for polymerization of olefins utilizing the supported catalystcomposition of the present invention producing a polymer having animproved product quality and morphology.

The present invention provides a supported catalyst composition forpolymerization of olefins comprising:

-   -   (i) a titanium compound, a magnesium compound and at least one        electron donor compound;    -   (ii) a chlorine containing polymer support; and    -   (iii) a cocatalyst comprising at least one aluminum compound,    -   wherein the magnesium loading in the final catalyst is between        0.20 and 6% by weight.

Moreover, the present invention provides a method for preparing asupported catalyst composition according to the present inventioncomprising the following steps:

-   -   (i) forming a catalytic precursor comprising a magnesium        compound, a titanium compound and at least one electron donor        compound;    -   (ii) mixing the catalytic precursor prepared in step (i) with a        polymer support in a solvent;    -   (iii) refluxing the mixture prepared in step (ii) for a certain        period of time;    -   (iv) optionally removing the solvent to form a solid powder of        the supported catalyst composition; and    -   (v) adding a cocatalyst comprising at least one aluminum        compound.

Further, the present invention provides a process for homopolymerizationof ethylene or copolymerization of ethylene with alpha-olefins and/ordiolefins by contacting ethylene or ethylene and alpha-olefins and/ordiolefins with a catalyst composition according to the presentinvention.

Surprisingly, it was found that a supported catalytic compositionaccording to the present invention shows an increased productivity inthe polymerization of olefins and has a low price in preparation.Moreover, the polymeric support will result in less product ash and inless catalyst residuals remaining in the polymer produced. Further, theproperties concerning the polymer produced with the catalyst compositionof the present invention show increased product clarity and resinmorphology. Without wishing to be bound to any theory, the functionalityof the polymeric support of the present invention seems to play a majorrole in anchoring or coordinating the catalyst precursor on the supportsurface and preventing precursor leaching which in turn would lead toform poor resin morphology as with polypropylene supports of the priorart.

DETAILED DESCRIPTION OF THE INVENTION

The catalyst precursor, in solid or dissoluted form, used in the presentinvention may be in principle identical to the one disclosed in U.S.Pat. No. 4,303,771.

This catalytic precursor has the formula Mg_(a)Ti(OR)_(b)X_(c)(ED)_(d)wherein R is an aliphatic or aromatic hydrocarbon radical having 1 to 14carbon atoms, or COR′ wherein R′ is an aliphatic or aromatic hydrocarbonradical having 1 to 14 carbon atoms; each OR group is the same ordifferent; X is Cl, Br, or I, or mixtures thereof; ED is electron donor;a is 0.5 to 56; b is 0, 1 or 2; c is 2 to 116; and d is greater than1.5a+2;

A titanium compound, which may be used in the method for preparing thesupported catalyst composition of the present invention may have theformula Ti(OR)_(a)X_(b) wherein R and X are defined as for the catalyticprecursor mentioned above; a is 0, 1, or 2; b is 1 to 4; a+b is 3 or 4.Suitable compounds are TiCl₃, TiCl₄, Ti(OC₆H₅)Cl₃, Ti(OC₂H₅)Cl₃,Ti(OCOCH₃)Cl₃ and Ti(OCOC₆H₅)Cl₃.

A magnesium compound useful in preparing the precursor may have theformula MgX₂ wherein X is defined as above. Suitable examples are MgCl₂,MgBr₂, and MgI₂. Anhydrous MgCl₂ is a preferred compound. About 0.5 to56, and preferably about 1 to 10, moles of the magnesium compound areused per mole of titanium compound. The magnesium loading on the finalcatalyst is between 0.20 and 6% by weight.

A suitable electron donor is an organic compound, which is liquid attemperatures in the range of about 0° C. to 200° C. It is also known asa Lewis base. The compounds used in the preparation of the catalystprecursor are soluble in the electron donor.

The electron donor may be an alkyl ester of an aliphatic or aromaticcarboxylic acid, an aliphatic ketone, an aliphatic amine, an aliphaticalcohol, an alkyl or a cycloalkyl ether, or mixture thereof, eachelectron donor having 2 to 20 carbon atoms. Among these electron donorsalkyl and cycloalkyl ethers having 2 to 20 carbon atoms; dialkyl,diaryl, and alkylaryl ketones having 3 to 20 carbon atoms; and alkyl,alkoxy, and alkylalkoxy esters of alkyl and aryl carboxylic acids having2 to 20 carbon atoms are preferred. The most preferred electron donor istetrahydrofuran. Other examples of suitable electron donors are methylformate, ethyl acetate, butyl acetate, ethyl ether, dioxane, di-n-propylether, dibutyl ether, ethyl formate, methyl acetate, ethyl anisate,ethylene carbonate, tetrahydropyran, ethyl propionate, hexyl ether,acetone, and methyl iso-butyl ketone.

The supports useful in the present invention are polymeric resinscomprising chlorinated polymers wherein polyvinyl chloride is thepreferred one. The supports have a particle size ranging between about 5and 1000 microns and the preferred size range is between 50 and 80microns. Furthermore, the supports have a particle pore volume of atleast about 0.1 cm³/g as well as surface area of at least about 0.2 cm².

On the final catalyst composition the titanium loading is preferablybetween about 0.15 and 5% by weight, and the electron donor loading ispreferably between 1 and 45% by weight.

The cocatalyst may comprise aluminum alkyls, aluminoxanes and/ormixtures thereof.

Further, the polymer support may further comprise an oxygen containingpolymer, such as polyketone and/or hydrolyzed polyketone.

Some polymeric supports may be incompatible with some electron donorsduring catalyst preparation. For instance, tetrahydrofuran can easilydissolves or agglomerate polyvinyl chloride. Therefore, a unique methodwas devised for preventing the support from getting agglomerated orswelled when contacted with the electron donor. First, the support isdried in vacuum between 40 and 90° C., then slurried in hydrocarbonmaterials such as isopentane, hexane, heptane, or isooctane. Thecatalyst precursor solution, which contains the electron donor, ispoured slowly on the support slurry and all materials are heated to 60°C. for from 15 minutes to 90 minutes. Mixing and stirring are employedcontinuously and constantly during the entire process. Washing withlight hydrocarbon solvents, such as hexane and isopentane at the end ofeach batch preparation is an option sometimes used, and otherwise thecomposition is dried directly without washing. This is performed tocompare catalyst activity and productivity utilizing both routes and forfacilitating the catalyst scaling up process later on. In both ways,active catalyst batches are obtained and may be excellently utilized ina process for slurry polymerization of olefins according to the presentinvention.

Initially, catalysts batches are dried with a slow flow of nitrogen overnight. Drying is later progressed to a vacuum drying to reduce lumpsformation and to shorten cycle time of catalyst preparation. Vacuumdrying is introduced after the majority of the liquid phase in the flaskwas evaporated. Catalyst drying time was varied with varying the desiredamounts of tetrahydrofuran on the catalyst. The performance of thecatalyst varies with varying tetrahydrofuran contents as well as withvarying magnesium/titanium ratio.

The catalyst composition according to the present invention may be alsoused for copolymerization of ethylene with alpha-olefin selected fromthe group comprising 1-butene, 1-hexene, and 1-octene and mixturesthereof.

EXAMPLES Example 1

Preparation of Catalyst Precursor

2.0 grams of anhydrous magnesium chloride, 1.16 ml of titaniumtetrachloride and 60 ml of dry THF were heated up to 55° C. in atwo-necked round bottom flask equipped with a condenser. The reactionwas conducted under an inert atmosphere with continuous stirring. After150 minutes, the content of the flask was cooled down, 10 ml of hexanewas added, and yellow solid powder precipitated in the bottom of theflask. The solid was washed four times with isopentane and dried withnitrogen flow overnight. The solid was analyzed to give a compositioncomprising Ti=5.4 wt %, Mg=5.8 wt % and THF=56.6 wt %.

Example 2

Preparation of Catalyst Composition

6.0 grams of polyvinyl chloride polymer was dried under vacuum at 50° C.for 30 minutes and placed in a two-necked round bottom flask. Thepolymer was slurried in hexane and 0.633 grams of the above dryprecursor powder (Example 1) slurried in 8 ml of THF were added slowlyto the polymer slurry. The temperature raised to 63° C. and thematerials were stirred and heated continuously for 30 minutes. Theexcess liquid was then drained and the remaining solid was washed withhexane and dried with nitrogen. The yellow catalyst was powdered andanalyzed to give a composition comprising Ti=0.16 wt %, Mg=0.39 wt % andTHF=1.55 wt %.

Example 3

Catalyst Performance—Ethylene Homopolymerization using CatalystComposition of Example 2

An ethylene polymerization was performed with the catalyst compositionof Example 2 at 15 bars of ethylene including three bars of hydrogenpartial pressure, and triethylaluminum alkyl (TEAL) was used as thepolymerization cocatalyst. The polymerization was run for one hour at atemperature of 85° C.

The polymerization run produced about 233 grams of homo-polyethyleneresin with a catalyst productivity of 2.5 kg PE/g cat-hr and an activityof 1474 kg PE/g Ti hr. The obtained polymer was a high-densitypolyethylene resin with a bulk density equal to 0.25 g/cc.

Example 4

Preparation of Catalyst Precursor

In a two-necked round bottom flask equipped with a condenser and amagnet stirrer, 2.0 grams of anhydrous magnesium chloride, 2.0 grams oftitanium tetrachloride and 70 ml of THF were placed. The materials wereheated to 60° C. and stirred for two hours until a clear yellow solutionwas formed.

Example 5

Preparation of Catalyst Composition

35 ml of the catalyst precursor of Example 4 was transferred slowly intoanother two-necked round bottom flask containing 6.0 grams of PVCpolymer slurried in hexane and heated to 60° C. The materials werestirred for 1 hour at the same temperature and were then cooled down.The solid was washed several times with hexane and dried with nitrogenat 60° C. The yellow catalyst powder was analyzed and the compositioncomprised of Ti=0.82 wt %, Mg=1.3 wt % and THF=16.7 wt.

Example 6

Catalyst Performance—Ethylene Homopolymerization Using CatalystComposition of Example 5

Ethylene polymerization was performed with the catalyst composition ofExample 5 at 15 bars of ethylene including three bars of hydrogenpartial pressure, and triethylaluminum alkyl (TEAL) was used as thepolymerization cocatalyst. The polymerization was run for one hour at atemperature of 85° C.

The polymerization run produced about 566 grams of homo-polyethyleneresin with a catalyst productivity of 9.7 kg PE/g cat-.hr and anactivity of 1185 kg PE/g Ti hr. The obtained polymer resin was ahigh-density homopolyethylene with a bulk density equal to 0.30 g/cc.

Example 7

Preparation of Catalyst Composition

3.0 grams of PVC polymer was dried under vacuum at 50° C. for 30 minutesand placed in a two-necked round bottom flask. The polymer was slurriedin hexane and 30 ml of the catalyst precursor of example 4 was added ontop of the polymer. The flask content was heated for 1 hour at 60° C.,then the excess liquid was drained and the remaining solid was washedwith hexane and dried under nitrogen at the same temperature. Thecatalyst composition was analyzed and comprised Ti=2.8 wt %, Mg=3.8 wt %and THF=30.7 wt %.

Example 8

Catalyst Performance—Ethylene Homopolymerization Using CatalystComposition of Example 7

Ethylene polymerization was performed with a catalyst compositon ofexample 7 at 15 bars of ethylene including three bars hydrogen partialpressure and triethylaluminum alkyl (TEAL) was used as thepolymerization cocatalyst. The polymerization was run for one hour at atemperature of 85° C.

The polymerization run produced about 572 grams of homo-polyethyleneresin with a catalyst productivity of 33.4 kg PE/g cat-hr and anactivity of 1194 kg PE/g Ti hr. The obtained polymer was a high-densitypolyethylene resin with a bulk density equal to 0.31 g/cc.

Example 9

Preparation of Catalyst Precursor

In a two-necked round bottom flask equipped with a condenser and amagnet stirrer, 1.0 grams of anhydrous magnesium chloride, 1.8 grams oftitanium tetrachloride and 70 ml of THF were placed. The materials wereheated to 60° C. and stirred for 90 minutes. A clear yellow solution wasformed.

Example 10

Preparation of Catalyst Composition

6.0 grams of polyvinyl chloride polymer was dried under vacuum at 50° C.for 30 minutes and placed in a two-necked round bottom flask. Thepolymer was slurried in hexane and the catalyst precursor of Example 9was added slowly to the polymer slurry. The temperature raised to 60° C.and the materials were stirred and heated continuously for 60 minutes.The excess liquid was then drained and the remaining solid was washedwith hexane and dried with nitrogen. The yellow catalyst powder wasanalyzed and the composition comprised Ti=2.3 wt %, Mg=1.8 wt % andTHF=30.3 wt %.

Example 11

Catalyst Performance—Ethylene Homopolymerization Using CatalystComposition of Example 10

Ethylene polymerization was performed with catalyst composition ofExample 10 at 15 bars of ethylene including three bars of hydrogenpartial pressure and triethylaluminum alkyl (TEAL) was used as thepolymerization cocatalyst. The polymerization was run for one hour at atemperature of 85° C.

The polymerization run produced about 320 grams of homo-polyethyleneresin with a catalyst productivity of 15.4 kg PE/g cat-hr and anactivity of 668 kg PE/g Ti hr. The obtained polymer was a high-densitypolyethylene resin with a bulk density equal to 0.11 g/cc.

Example 12

Preparation of Catalyst Precursor

In a two-necked round bottom flask equipped with a condenser and amagnet stirrer, 2.0 grams of anhydrous magnesium chloride, 2.0 grams oftitanium tetrachloride and 70 ml of THF were placed. The materials wereheated to 60° C. and stirred for 90 minutes. A clear yellow solution wasformed.

Example 13

Preparation of Catalyst Composition

6.0 grams of PVC polymer was dried under vacuum at 50° C. for 30 minutesand placed in a two-necked round bottom flask. The polymer was slurriedin hexane and the catalyst precursor of Example 12 was added slowly tothe polymer slurry. The temperature was raised to 60° C. and thematerials were stirred and heated continuously for 60 minutes, thendried with nitrogen under vacuum. The yellow catalyst powder wasanalyzed and the composition comprised Ti=0.94 wt %, Mg=2.9 wt % andTHF=43.0 wt %.

Example 14

Catalyst Performance—Ethylene Homopolymerization Using CatalystComposition of Example 13

Ethylene polymerization was performed with catalyst composition ofExample 13 at 15 bars of ethylene including three bars of hydrogenpartial pressure and triethylaluminum alkyl (TEAL) was used as thepolymerization cocatalyst. The polymerization was run for one hour at atemperature of 85° C.

The polymerization run produced about 494 grams of homo-polyethyleneresin with a catalyst productivity of 9.7 kg PE/g cat-hr and an activityof 1031.3 kg PE/g Ti hr. The obtained polymer was a high-densitypolyethylene resin with a bulk density equal to 0.24 g/cc.

Example 15

Preparation of Catalyst Precursor

In a two-necked round bottom flask equipped with a condenser and amagnet stirrer, 2.0 grams of anhydrous magnesium chloride, 1.4 grams oftitanium tetrachloride and 70 ml of THF were placed. The materials wereheated to 60° C. and stirred for 90 minutes. A clear yellow solution wasformed.

Example 16

Preparation of Catalyst Composition

3.0 grams of PVC polymer (sieved at 120 mesh) was dried under vacuum at50° C. for 30 minutes and placed in a two-necked round bottom flask. Thepolymer was slurried in a hexane and the catalyst precursor of Example15 was added slowly to the polymer slurry. The temperature was raised to60° C. and the materials were stirred and heated continuously for 30minutes, then dried with nitrogen under vacuum. The yellow catalystpowder was analyzed and the composition comprised Ti=2.87 wt %, Mg=4.35wt % and THF=45.0 wt %.

Example 17

Catalyst Performance—Ethylene Homopolymerization Using CatalystComposition of Example 16

Ethylene polymerization was performed with catalyst composition ofexample 16 at 15 bars of ethylene including three bars of hydrogenpartial pressure and triethylaluminum alkyl (TEAL) was used as thepolymerization cocatalyst. The polymerization was run for one hour at atemperature of 85° C.

The polymerization run produced about 263 grams of homo-polyethyleneresin with a catalyst productivity of 15.8 kg PE/g cat-hr and anactivity of 549.1 kg PE/g Ti hr. The obtained polymer was a high-densitypolyethylene resin with a sieved bulk density equal to 0.28 g/cc.

The features disclosed in the foregoing description and/or in the claimsmay, both separately and in any combination thereof, be material forrealising the invention in diverse forms thereof.

1. A supported catalyst composition for polymerization of olefinsconsisting essentially of: (i) a titanium compound of the selected fromthe group consisting of TiCl₃, TiCl₄, Ti(OC₆H₅)Cl₃, Ti(OC₂H₅)Cl₃,Ti(OCOCH₃)Cl₃ and Ti(OCOC₆H₅)Cl₃, a magnesium compound and at least oneelectron donor compound; (ii) a polyvinyl chloride support; and (iii) acocatalyst comprising at least one aluminum compound; wherein themagnesium loading on the catalyst composition is between about 0.20 and6% by weight.
 2. The supported catalyst composition according to claim1, wherein the titanium compound is titanium tetrachloride.
 3. Thesupported catalyst composition according to claim 2, wherein themagnesium compound is magnesium chloride.
 4. The supported catalystcomposition according to claims 3, wherein said electron donor istetrahydrofuran.
 5. The supported catalyst composition according toclaim 4, wherein the polyvinyl chloride support has a particle sizebetween about 5 μm and about 1000 μm.
 6. The supported catalystcomposition according to claim 5, wherein the polyvinyl chloride supporthas a pore volume of at least about 0.1 cm³/g and a surface area of atleast about 0.2 m²/g.
 7. The supported catalyst composition according toclaim 5, wherein the titanium loading on the catalyst composition isbetween about 0.15 and 5% by weight.
 8. The supported catalystcomposition according to claim 6, wherein the titanium loading on thecatalyst composition is between about 0.15 and 5% by weight.
 9. Thesupported catalyst composition according to claim 8, wherein theelectron donor loading on the catalyst composition is between about 1and 45% by weight.
 10. The supported catalyst composition according toclaim 9, wherein the cocatalyst comprises an aluminum alkyl or analuminoxane.
 11. A method for preparing a supported catalyst compositioncomprising the following steps: (i) mixing a magnesium compound, atitanium compound selected from the group consisting of TiCl₃, TiCl₄,Ti(OC₆H₅)Cl₃, Ti(OC₂H₅)Cl₃, Ti(OCOCH₃)Cl₃ and Ti(OCOC₆H₅)Cl₃ and atleast one electron donor compound to form a catalyst precursor; (ii)mixing the catalytic precursor prepared in step (i) with a polyvinylchloride support in a hydrocarbon liquid; (iii) removing the hydrocarbonliquid from the product of step (ii) and recovering a supportedcatalyst; and (iv) adding a cocatalyst comprising at least one aluminumcompound to the supported catalyst of step (iii).
 12. The methodaccording to claim 11, wherein the mixture of step (ii) is heated atabout 60° C. for about 15 to 90 minutes.
 13. The method according toclaim 12, wherein said hydrocarbon liquid is hexane, isooctane orisopentane.
 14. A process for the homopolymerization of ethylene or thecopolymerization of ethylene with an alphaolefin or a diolefin toproduce a polymer, comprising contacting ethylene or ethylene and analphaolefin or a diolefin with a supported catalyst in the presence of acocatalyst, said supported catalyst prepared according to a processcomprising: (i) treating a polyvinyl chloride support with a catalystprecursor comprising a mixture of a titanium compound selected from thegroup consisting of TiCl₃, TiCl₄, Ti(OC₆H₅)Cl₃, Ti(OC₂H₅)Cl₃,Ti(OCOCH₃)Cl₃ and Ti(OCOC₆H₅)Cl₃, a magnesium compound and at least oneelectron donor in a hydrocarbon liquid; (ii) removing said hydrocarbonliquid from the product of step (i).
 15. The process of claim 14,wherein said titanium compound is titanium tetrachloride and saidmagnesium compound is magnesium chloride.
 16. The process of claim 15,wherein said electron donor is tetrahydrofuran.
 17. The process of claim16, wherein said polyvinyl chloride support has a particle size betweenabout 5 and 1,000 μm, a pore volume of at least about 0.1 cm³/g and asurface area of at least about 0.2 m²/g.
 18. The process of claim 17,wherein the product of step (i) is heated at about 60° C. for about 15to 90 minutes.
 19. The process of claim 18, wherein the cocatalystcomprises an aluminum alkyl or an aluminoxane.